A facebow is used in conjunction with a bite fork and transfer jig to orient the molds made of a person's upper and lower tooth structures on a dental articulator. The molds are positioned in an articulator for analysis of the person's bite. The facebow, transfer jig and bite fork help properly position the molds in the articulator to replicate the person's bite. The alignment of the bite fork in the person's mouth is important to insure the proper orientation of the molds in the dental articulator. The facebow helps properly orient the bite fork.
As is known in the art, the bite fork is adjustably attached to the transfer jig, and the transfer jig is fixed to the facebow. The first two reference points are created by the engagement of the facebow arms in the patient's ears. However, a vertical axis dimension, or third point of reference, must be used to thoroughly orient the models in the dental articulator. The facebow is aligned with the third point of reference by generally pivoting through a vertical arc in front of the patient's face to a particular position in alignment with the third reference point, and then fixing the bite fork to the transfer jig. This fixes the orientation of the bite fork in alignment with the third point of reference.
The third reference, or anterior reference point, is generally positioned by measuring 43 millimeters above the lateral incisor edge on the right, central or lateral incisors. The anterior reference point is generally positioned just underneath the right eye of the patient. The location of the reference point is typically noted by a mark, such as an ink mark, on the patients face.
To align the facebow with the third point of reference, the facebow is positioned on the patient's face, with the transfer jig attached to the facebow. The third point of reference is obtained by aligning the facebow with the anterior reference point on the patient's face. The facebow is moved through a vertical arc in front of the patient's face, pivoting about the engagement of the facebow with the patient's ears.
Typically, the facebow is properly positioned in alignment with the anterior reference point by using a reference pointer which swings inwardly from one of the facebow arms toward the patient's face. The end of the pointer is aligned with the reference point on the patient's face to properly position the facebow. Since the anterior reference point is generally just underneath the right eye of the patient, the patient can be disturbed by the movement of the pointer towards the anterior reference point for fear that the pointer will contact the patient's eye. This makes the procedure uncomfortable for the patient, and often results in inaccurate facebow placement since the patient frequently moves in response to the use of the pointer.
Dental professionals, due to these issues related to the use of the pointer, often do not use the pointer at all, but rather just position the facebow in the approximate position that the pointer would place it. This general positioning is not precise, and often leads to misalignment of the molds in the articulator.
Another issue with respect to existing facebows is that it is difficult to properly position the left and right arms for engagement with the patient's ears and at the same time keep the facebow centered on the patient's face. This is difficult since the arms on many presently available facebows move independently of one another. If the facebow is not perfectly centered on the patient's face, the alignment of the resulting molds in the articulator can be inaccurate. Even in available facebows where the arms do not move independently (where the arms must be made in left and right pairs), it is difficult to fix the position of the arms with respect to one another. Additionally, compass-type facebows cause the transfer jig to be misaligned forwardly or rearwardly with respect to the patient's face as the facebow arms are opened and closed.
A further issue with respect to existing facebows is the inaccurate engagement of the facebow with the patient's ears. Each arm of the presently-available facebow typically has an ear piece positioned at its tip to insert into the patient's ear canal. However, the existing ear pieces are difficult to repeatably position in a patient's ear to obtain a consistent engagement therein. In other words, the ear pieces can be positioned in a patient's ear in several different ways and result in several different alignments, one corresponding with each different plug positioning.
Finally, the sterilization of the existing facebows are often inconvenient in that the facebow either must be taken apart to fit into an autoclave, or because not all pieces of the facebow can withstand the autoclave process.
It is with the above limitations of the presently available facebows that the invention described and claimed herein was developed.